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Homework Help: Vertically Thrown Rock

  1. Oct 19, 2011 #1
    1. The problem statement, all variables and given/known data

    Brad tosses a rock straight up at 33.4 m/s. What is the rock's velocity after 2.1 seconds?


    2. Relevant equations

    V=Vo+at
    X=Xo+Vot+1/2at^2
    V^2=Vo2+2a(X-Xo)

    3. The attempt at a solution

    I used the first equation. V=33.4m/s+9.8(2.1) 9.8 being the acceleration due to gravity. The hint says 'Final velocity equals the initial velocity plus the product of acceleration due to gravity (g) multiplied by the time.' I kept getting the incorrect answer of 54m/s.
     
  2. jcsd
  3. Oct 19, 2011 #2
    When going up the pull of the Earth will retard it so put '-9.8'.
     
  4. Oct 19, 2011 #3
    Thank You! I got the answer right! But what equation would I use to find the maximum height of the rock?
     
    Last edited: Oct 19, 2011
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